I'm looking to buy a commuter car. What's better on gas in a Civic a VTEC
 

engine or Twin Cam?

VTEC just means that the Civic has Variable valve Timing and Lift Electronic Control technology and comes in both SOHC ( single over head cam) and DOHC ( aka twin cam or dual overhead cam). It doesn't hurt gas mileage to have VTEC.It actually improves gas mileage by making the engine more efficient at lower rpm's . If you are really looking for better gas mileage, go for the smaller engines (i.e. 1.6litre vs. 2.0litre) w/ VTEC.

Which Civic VTec? year? model? In the US all Civic engines are SOHC except the DOHC B16a on certain Del Sol and the the 2000 Si typeR.There is a economy Vtec (I think 8 to 12 valves), Vtec-e (economy, 01-06 EX, 12 to 16 valves), the regular Vtec (performance), twin-cam (ZC engine, not on US domestic cars) and the twin-cam Vtec (B16A, valve timing and cams, real performance).